IntroductionThe remarkable interest of neuropathologists in the relatively rare conditions generically called Schilder's disease or diffuse sclerosis is reflected by the disproportionately large number of publications. Numerous authors have made valuable contributions, aimed at an understanding of the causes of these diseases, which ultimately enabled Poser and van Bogaert1,2 to arrive at a lucid histologic system of classification incorporating etiologic and prognostic implications. In summary, Poser2 proposed that these diseases fall into 3 different categories, (1) the myelinoclastic group, closely related to multiple sclerosis; (2) the dysmyelinating group or leukodystrophies, probably due to some inherited enzymatic defects; (3) the leukoencephalitides, possibly of viral origin. While this now universally accepted system is of immeasurable value to the pathologist, it is of little help to the clinician in differentiating these clinically similar but etiologically and pathogenically divergent conditions. Obviously, a correct clinical diagnosis will not only permit a more